The present invention relates to a device and method that augments a user's strength and aids in the prevention of injury during the performance of certain strength-requiring tasks. More particularly, the present invention relates to a device suitable for use by a person engaging in heavy tool use or weight bearing tasks, comprising a set of artificial limbs and related control systems that potentiate improved function of the person's appendages for activities including, but not limited to, greater strength and endurance in the wearer's arms, or allowing for more weight to be carried by the wearer while walking.
Wearable exoskeletons have been designed for medical, commercial and military applications. Medical exoskeletons are designed to help restore a user's mobility. Commercial and military exoskeletons help prevent injury and augment the user's strength. Commercial exoskeletons are used to alleviate loads supported by workers during their labor, thereby preventing worker injuries and increasing their stamina and strength.
Initial testing has been performed using an exoskeleton outfitted with a tool holding arm that supports the weight of the tool. These devices reduce user fatigue by providing tool holding assistance. The tool holding arm transfers the vertical force required to hold the tool through the legs of the exoskeleton rather than through the user's arms. One problem with this exoskeleton use is that the tool is held in front of the exoskeleton's legs. This produces a forward falling torque about the exoskeleton hip joint that must be resisted by the user. Users tend to lean back excessively to compensate for this forward torque which places unwanted loads on the user's body.
In order to reduce this load on the user's body, a counteracting torque must be applied at the hip joint. Using a spring to create this torque will generate too great a torque in the swing phase (unless the spring can be disengaged, and such mechanisms are generally heavy and complex). Although this can be avoided with an actuated hip joint, such a design requires constant power consumption while standing, requiring heavy batteries and negating the advantage. For an exoskeleton with non-actuated hips, a weight must be installed behind the user to provide the necessary torque to counteract the weight of the tool and minimize the load felt by the user. A counter torque can be produced with a range of weights and moment arms: lighter weights require longer moment arms and heavier weights require shorter moment arms. These, however, are undesirable because heavier counter weights will make the exoskeleton heavier and harder to move, while longer moment arms reduce maneuverability in what is often a confined work environment.
For at least these reasons, there exists a need to develop a device and method that allow for a reduction in the forward hip torque in an exoskeleton with a tool-holding arm.